In recent years, a polishing apparatus has been used to polish a surface of a substrate such as a semiconductor wafer. The polishing apparatus is configured to include: a polishing table onto which a polishing pad for polishing a substrate is positioned and attached; a motor rotating the polishing table; a top ring holding and pressing the substrate against the polishing pad; and the like.
When such a polishing apparatus polishes a large number of substrates, the polishing surface of a polishing pad is worn, and thus the polishing pad is replaced at regular intervals. The polishing pad is a consumable material having a high replacement frequency for the polishing apparatus, thus requiring high working efficiency for replacing polishing pads.
The polishing pad is replaced, for example, by hand of a worker. The polishing pad is commonly formed into the same shape as that of an attachment surface of the polishing table. Here positioning and attaching the polishing pad onto the polishing table in a state of being shifted with respect to the attachment surface of the polishing table may cause adverse effects on polishing performance. Therefore, the polishing pad is required to be positioned on and attached to the polishing table so as to match the attachment surface with the outer periphery. However, this work is visually carried out by workers, thereby causing a problem of increasing attachment time and reducing attachment productivity for inexperienced workers.
In light of this, there is known a polishing pad fixing mechanism for fixing a polishing pad to a platen (polishing table) in an easy manner and with a high accuracy, wherein the polishing pad is attached onto a support base having a guide ring for positioning the polishing pad, and the support base is fixed to the platen (see Japanese Patent Laid-Open No. 2004-259814).
By the way, in the polishing pad attachment process, air may enter between a front surface of the polishing table and a rear surface of the polishing pad, forming air pockets. Thereby, an air trapped portion of the polishing pad slightly rises with respect to the polishing table. The projected portion of the polishing pad may affect the substrate polishing process. Therefore, when air pockets are formed between the polishing pad and the polishing table, the polishing pad needs to be removed from the polishing table and discarded, and then a new polishing pad needs to be attached to the polishing table again. In light of this, in order to prevent air pockets from forming, the polishing pad is attached to the polishing table by pressing the polishing pad against the polishing table starting with one peripheral portion thereof, then gradually moving toward a central portion thereof, to extrude air pockets therefrom.
However, it is difficult to completely extrude air pockets before attaching the polishing pad to the polishing table. Note that a currently available wafer has a maximum diameter of 300 mm. It the wafer diameter increases in the future, the size of the polishing pad may increase accordingly. Such an increase in size of the polishing pad may make it more difficult for even experienced workers to attach the polishing pad to the polishing table without forming air pockets.